import math
x1,y1,x2,y2 = map(float,input().split())
ans = math.sqrt((x2-x1)**2+(y2-y1)**2) 
print(round(ans,8)) import math math x1,y1,x2,y2 = map(float,input().split()) x1 map(float,input().split()) map float input().split() ().split () input split y1 x2 y2 ans = math.sqrt((x2-x1)**2+(y2-y1)**2) ans math.sqrt((x2-x1)**2+(y2-y1)**2) math.sqrt math sqrt (x2-x1)**2+(y2-y1)**2 (x2-x1)**2 x2-x1 x2 x1 2 (y2-y1)**2 y2-y1 y2 y1 2 print(round(ans,8)) print round(ans,8) round ans 8 y2 = map(float,input().split()) map(float,input().split()) y2 y1,x2,y2 = map(float,input().split()) map(float,input().split()) y1 x1,y1,x2,y2 = map(float,input().split()) map(float,input().split()) x1 x2,y2 = map(float,input().split()) map(float,input().split()) x2 ans = math.sqrt((x2-x1)**2+(y2-y1)**2) math.sqrt((x2-x1)**2+(y2-y1)**2) ans
import math
x1,y1,x2,y2 = map(float,input().split())
ans = math.sqrt((x2-x1)**2+(y2-y1)**2) 
print(round(ans,8))
